Circuits and methods for repairing defects in memory devices

ABSTRACT

Some embodiments of the invention include a memory device has a number of memory segments connected to a supply source through a supply control circuit. The supply control circuit isolates a selected memory segment from the supply source when the selected memory segment is defective. The memory device replaces a defective memory segment with a redundant segment. Other embodiments are described and claimed.

RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.10/609,312, filed Jun. 24, 2003 now U.S. Pat. No. 7,437,632, which isincorporated herein by reference.

FIELD

The embodiments of the invention relate generally to semiconductordevices, more particularly to repairing defects in memory devices.

BACKGROUND

Memory devices reside in many computers and electronic products to storedata.

A typical memory device has many memory cells and some redundant (spare)cells. When some of the memory cells are defective, the defective memorycells can be replaced with redundant cells to repair the memory device.This repairing method saves the entire memory device when only a fewmemory cells are defective.

Certain defects are repairable. Some defects are irreparable, causingthe entire memory device to be discarded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a memory device according to an embodiment of theinvention.

FIG. 2 shows a flow chart of a method of repairing a memory deviceaccording to an embodiment of the invention.

FIG. 3 shows a portion of the memory device of FIG. 1.

FIG. 4 shows a portion of a memory device having a defective memorysegment according to an embodiment of the invention.

FIG. 5 shows an alternative embodiment of the portion of the memorydevice of FIG. 3.

FIG. 6 shows a switching unit and multiple memory cells according to anembodiment of the invention.

FIG. 7 shows the switching unit and the multiple memory cells of FIG. 6in which at least one of the memory cells has a defect.

FIG. 8 shows multiple memory cells connected between two switching unitsaccording to an embodiment of the invention.

FIG. 9 shows a switching unit and a memory cell according to anembodiment of the invention.

FIG. 10 shows the switching unit and the memory cell of FIG. 9 in whichthe memory cell has a defect.

FIG. 11 shows a memory cell connected between two switching unitsaccording to an embodiment of the invention.

FIG. 12 shows a system according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following description and the drawings illustrate specificembodiments of the invention sufficiently to enable those skilled in theart to practice the embodiments of the invention. Other embodiments mayincorporate structural, logical, electrical, process, and other changes.In the drawings, like numerals describe substantially similar componentsthroughout the several views. Examples merely typify possiblevariations. Portions and features of some embodiments may be included inor substituted for those of others. The scope of the inventionencompasses the full ambit of the claims and all available equivalents.

FIG. 1 shows a memory device according to an embodiment of theinvention. Memory device 100 includes a memory array 101 and a redundantarray 102. Memory array 101 includes a number of memory segments 111.Redundant array 102 includes a plurality of redundant segments 122. Eachof the redundant segments 122 can replace a defective memory segmentamong memory segments 111.

A read/write circuit 104 accesses memory array 101 using memory accesssignals DR in response to input address INADDR signals provided by anaddress register 106. The INADDR signals are derived from addresssignals A0-AX provided to address register 106 from address lines 108.Data signals DQ0-DQN on data lines 140 represent data transferred to andfrom memory array 101 and redundant array 102 via a data path circuit133. Lines 141 carry data transferred between memory array 101 and datapath circuit 133. Lines 142 carry data transferred between redundantarray 101 and data path circuit 133.

A memory controller 118 controls the operations of memory device 100based on control signals CTL1-CTLM on control lines 120.

A programmable unit 130 includes a plurality of programmable elements132. Examples of programmable elements 132 include fuses, anti-fuses,and flash EEPROM cells. Other types of programmable elements can be alsoused. Programmable elements 132 can be programmed (configured) to storeaddresses of one or more defective memory segments of memory array 101.Programmable unit 130 provides programmed address signals PROGADDR,which represent addresses of defective memory segments of memory array101.

A redundancy controller 135 controls access to redundant array 102 usinga match signal MATCH and redundant access signals RA based on inputaddress signals INADDR and the programmed address signals PROGADDR.Redundancy controller 135 also controls the states (signal levels) of aplurality of select signals S1 through SN based on the PROGADDR signals.

Memory device 100 has supply nodes 151 and 152 for receiving supply(power) sources Vcc and Vss. In some embodiments, Vcc is a positivevoltage and Vss is ground. A supply generator 145 generates supplyvoltages V1, V2 on supply nodes 161 and 162. Each of the V1 and V2 isfunction of Vcc and Vss. In embodiments represented by FIG. 1, V1 equalsVcc, V2 equals Vss, and Vss is ground. In some embodiments, V1 and V2are non-ground and V1 is greater than V2. In some other embodiments,supply generator 145 is omitted, node 151 connects directly to node 161and node 152 connects directly to node 162.

During an operation of memory device 100, the INADDR signals, derivedfrom the A0-AX signals, represent addresses of memory cells 111 to beaccessed. Redundancy controller 135 compares the INADDR signals and thePROGADDR signals. A mismatch between these signals indicates that theaddress represented by the INADDR signals correspond to a non-defective(good) memory segment of memory array 101. A match between these signalsindicates that the address represented by the INADDR signals correspondto a defective memory segment of memory array 101.

In the mismatch case, redundancy controller 135 keeps both MATCH and RAsignals inactivated. Write/read circuit 104 accesses memory cells ofmemory array 101 based on input addresses provided by address register106. Data represented by the DQ0-DQN signals are transferred to and frommemory array 101 via lines 141.

In the match case, redundancy controller 135 activates the MATCH signalto prevent write/read circuit 104 from accessing memory array 101, andactivates the RA signal to access redundant array 102 based on theINADDR signals. Data represented by the DQ0-DQN signals are transferredto and from redundant array 101 via lines 142.

A supply control circuit 150 controls supply sources provided to memoryarray 101. In some embodiments, the supply sources include current, orvoltage, or both. In embodiments represented by FIG. 1, the supplysource includes either one of or a combination of Vcc, Vss, V1 and V2.Supply control circuit 150 receives the S1-SN signals from redundancycontroller 135 to control the supply sources provided to memory array101. When memory array 101 has a defective memory segment, supplycontrol circuit 150 isolates (disconnects) the defective memory segmentfrom the supply source to save power.

Memory device 100 also has other circuit elements, for example,decoders, sense amplifiers, which are not shown for simplicity. Further,each of the INADDR, PROGADDR, DR, and RA signals represents multiplesignals carried by multiple lines; however, each of these signals isshown as a single signal on a single line for simplicity.

Memory device 100 can be a static random access memory device (SRAM), adynamic random access memory device (DRAM), a flash memory device, orother types of memory devices.

FIG. 2 shows a flow chart of a method of repairing a memory deviceaccording to an embodiment of the invention. Method 200 can be used torepair memory device 100 (FIG. 1). In FIG. 2, box 205 of method 200determines a condition of a memory array such as memory array 101. Ifthe memory array has a defective memory segment, box 210 identifies theaddress of the defective memory segment. Box 215 stores the address ofthe defective memory segment. The address can be stored in a unit suchas programmable unit 130 (FIG. 1). Box 220 isolates the defective memorysegment from a supply source such as supply source Vcc, Vss, V1 or V2 tosave power. Box 225 replaces the defective memory segment with aredundant segment such as redundant segment 122 (FIG. 1) so that theoriginal capacity of the memory array remains unchanged.

Determining the condition of the memory array (box 205) can be achievedby various techniques. One of the techniques involves detecting for adefect during a test in which test data is written to the memory array.The data is subsequently read from the memory array and is compared withthe test data to detect for errors. Certain errors indicate a defectexisted in the memory array. The errors are analyzed to determine thetype of defect. In some embodiments, the errors are analyzed bycomparing them with known errors. The known errors are caused by knowntypes of defects. For example, certain known errors are caused bydefects that involve charge leakage between adjacent memory segments ormemory cells of the memory array. Some known errors are caused bydefects that involve circuit shorts between internal nodes of the memoryarray in which the internal nodes connect to the supply source suppliedto the memory array.

After the type of defect is determined and the address of the defectivememory segment is identified (box 210), the address is stored. Storingthe address (box 215) can be done by programming elements such asprogrammable elements 132 (FIG. 1). In some embodiments, the programmingincludes blowing fuses, applying programming voltage to anti-fuses, orother programming method. Based on the address programmed in theprogramming unit, the defective memory segment is isolated from thesupply source.

Isolating the defective memory segment from the supply source (box 220)can be achieved by a unit such as supply control circuit 150 (FIG. 1).In some embodiments, isolating the defective memory segment from thesupply source includes preventing the defective memory segment fromdrawing current in a current path supplied to the defective memorysegment. In other embodiments, isolating the defective memory segmentfrom the supply source includes electrically disconnecting the defectivememory segment from a supply voltage. When the defective memory segmentis isolated, it is replaced by a redundant segment.

In some embodiments, replacing the defective memory segment (box 225)includes rerouting an access route connected to the defective memorysegment with an access route connected to a redundant segment. Thererouting can be performed by a redundancy controller similar toredundancy controller 135 (FIG. 1).

FIG. 3 shows a portion of the memory device of FIG. 1. Memory array 101connects to supply node 301 via a supply path 333. Supply path 333represents a combination of supply paths 361, 362, and 363. Each of thesupply paths 361, 362, and 363 connects between supply node 301 and oneof the first internal nodes 311, 321, and 331. Supply control circuit150 connects in supply path 333 and in series with memory array 101between supply node 301 and supply node 302. Supply node 301 receives asupply voltage V1. Supply node 302 receives to a supply voltage V2. V1and V2 correspond to V1 and V2 of FIG. 1. In some embodiments, V1 is apositive voltage and V2 is ground.

Memory array 101 includes a number of memory segments 310, 320, and 330.For simplicity, FIG. 3 shows only three memory segments. However, memoryarray 101 can have N memory segments where N is an integer. In FIG. 3, Nequals three.

Memory segments 310, 320, and 330 connect in parallel with each otherbetween first internal nodes 311, 321, and 331 and a plurality of secondinternal nodes 312, 322, and 332. Each of the memory segments connectsbetween one of the first internal nodes and one of the second internalnodes. For example, memory segment 310 connects between internal nodes311 and 312.

Each of the memory segments includes a number of memory cells 315arranged in rows and columns. For example, memory segment 310 has memorycells 315 arrange in rows Row0, Row1, and Row2 and in columns Col0,Col1, and Col3. In some embodiments, memory segments 310, 320, and 330have equal number of memory cells. In this specification, a memory cellgroup refers to either each of the rows or each of the columns. Memorycells 315 connect to word lines WL and bit lines BL.

Supply control circuit 150 includes a number of switching units 351,352, and 353 and input nodes to receive the select signals S1-SN. Insome embodiments, the number of the switching units equals N, which isthe number of memory segments of memory array 101. Each of the switchingunits connects in one of the supply path 361, 362, and 363 and in serieswith a corresponding memory segment and a corresponding internal node.For example, switch unit 351 connects in supply path 361 and in serieswith corresponding memory segment 310 corresponding and internal node311.

Each switching unit has an enable mode and a disable mode; these modesare controlled by the S1-SN signals. In some embodiments, one of theS1-SN signals controls one of the switching units to switch theswitching unit between the enable and disable modes. In someembodiments, the enable and disable modes of the switching units dependon the states of the S1-SN signals. For example, when the S1 signal isused to control switching unit 310, a low signal level of the S1 signalcan be used to switch switching unit 351 to the enable mode; and a highsignal level of the S1 signal can be used to switch switching unit 351to the disable mode.

When a switching unit is in the enable mode, it allows the correspondingmemory segment to receive the supply sources from supply nodes 301 and302. When a switching unit is in the disable mode, it prevents thecorresponding memory segment from receiving the supply source fromsupply nodes 301 and 302. For example, when switching unit 351 is in theenable mode, it allows memory segment 310 to receive V1 and V2 fromsupply nodes 301 and 302; when switching unit 351 is in the disablemode, it prevents memory segment 310 from receiving V1 and V2 fromsupply nodes 301 and 302.

In some embodiments, when a switching unit is in the enable mode, itconnects supply node 301 to the corresponding internal node, therebycreating a conductive path between the supply node and the correspondinginternal node. When a switching unit is in the disable mode, it isolatessupply node 301 from the corresponding internal node, therebyprohibiting a conductive path from being created between the supply nodeand the corresponding internal node. In some embodiments when aswitching unit isolates the corresponding memory segment from supplynode 301, the switching unit electrically disconnects the correspondinginternal node from supply node 301.

In some embodiments, each switching unit isolates the correspondingmemory segment from supply node 301 when the corresponding memorysegment has a defect. The defect may be caused by a circuit shortbetween the first and second internal nodes connected to the same memorysegment. For example, when a circuit short exists between internal nodes311 and 312 connected to memory segment 310, switching unit 351 isolatesmemory segment 310 from supply node 301. Memory segments 320 and 330remain connected to supply node 301 by switching units 352 and 353.

In some embodiments, each of the switching units 351, 352, and 353 has aresistance such that the voltage of the corresponding internal node(311, 321, or 331) is reduced from an initial voltage value to a reducedvoltage value when a defect exists in the corresponding memory segment(310, 320, or 330). In some embodiments, the reduced voltage value issufficient to indicate a circuit short between the correspondinginternal node and supply node 302.

FIG. 4 shows a portion of a memory device having a defective memorysegment according to an embodiment of the invention. Portion 400includes elements similar to the elements of the portion of memorydevice 100 shown in FIG. 3. In FIG. 4, portion 400 includes supply nodes401 and 402, a memory array 401 having a number of memory segments 410,420, and 430, and a supply control circuit 450 having a number ofswitching units 451, 452, and 453. In FIG. 4, each of the switchingunits 451, 452 and 453 is controlled by one of the select signals S1-SN.For example, switching unit 451 is controlled by the S1 signal.

In FIG. 4, each of the memory segments has a number of memory cells 415and connects between one of the internal nodes 411, 421, 431 and one ofthe internal nodes 412, 422, and 432. In some embodiments, memorysegments 410, 420, and 430 have equal number of memory cells.

At least one of the memory segments 410, 420, and 430 is defective. Forexample, among the memory segments, memory segment 410 is defective andmemory segments 420 and 430 are not defective. A resistor symbol R1represents a defect in memory segment 403. R1 is not an actual resistor;R1 is shown for the purposes of showing a defect. In some embodiments,R1 represents a defect caused by a circuit short between internal nodes411 and 412.

The each of the non-defective memory segments 420 and 430 has aresistance measured between the corresponding internal nodes. Forexample, each of the memory segments 420 and 430 has a resistance R2,which is measured between internal nodes 421 and 422, or betweeninternal nodes 431 and 432.

In some embodiments, the resistance measured between the correspondinginternal nodes of a defective memory segment is unequal to theresistance measured between the corresponding internal nodes of anon-defective memory segment. Thus, in FIG. 4, R1 is unequal to R2.

Supply control circuit 450 isolates a memory segment of memory array 403from the supply node 401 when the memory segment is defective. In theabove example where memory segment 410 is defective, switching unit 451isolates memory segment 410 from supply node 401.

FIG. 5 shows an alternative embodiment of the portion of the memorydevice of FIG. 3. For simplicity, similar elements in FIG. 3 and FIG. 5have similar reference numbers. In FIG. 5, supply control circuit 550includes switching units 551, 552, and 553 in addition to switching unit351, 352, and 353. Thus, each memory segment has two correspondingswitching units connected to it.

Each of the switching unit 551, 552, and 553 connects between supplynodes 302 and one of the internal nodes 312, 322, and 332 and has enableand disable modes similar to that of each of switching units 351, 352,and 353 (FIG. 3).

In some embodiments, all of the switching units of FIG. 5 have similarconstructions and the select signals S1-SN can be used to control all ofthe switching units. In other embodiments, switching units 351, 352, and353 have different constructions from switching units 551, 552, and 553.In these embodiments, the S1-SN signals can be used to control switchingunits 351, 352, and 353 and the derivatives of the S1-SN signals can beused to control switching units 551, 552, and 553. For example, invertedversions of the S1-SN signals can be used to control switching units551, 552, and 553.

In some embodiments, at least one of the memory segments 310, 320, and330 has a defect such as that of memory segment 410 (FIG. 4). In somecases, the defect is caused by a circuit short between internal nodes,for example, between internal nodes 311 and 312. In FIG. 5, when amemory segment has a defect, either one or both of the correspondingswitching units is switched to the disable mode to isolate the memorysegment from one or both of the supply nodes 301 and 302. For example,when memory segment 310 has a defect, one or both of the switching units351 and 551 is switched to the disable mode to isolate memory segment310 from one or both of the supply nodes 301 and 302.

FIG. 6 shows a switching unit and multiple memory cells according to anembodiment of the invention. Switch unit 651 correspond to one of theswitching units 351, 352, and 353 (FIG. 3). Memory cells 615 correspondto memory cells 315 (FIG. 3). Thus, memory cells 615 of FIG. 6correspond to either memory cells of one of the rows Row1, Row2, andRow3 or memory cells of one of the columns Col0, Col1, and Col2 (FIG.3). In some embodiments, memory cells 315 are static memory cells.

Switching unit 651 connects between a first supply node 601 and aninternal node 611. Each of the memory cells 615 connects between aninternal node 611 and an internal node 612. A second supply node 602connects to internal node 612. The internal nodes and the supply nodesin FIG. 6 correspond to that of FIG. 3. Switching unit 651 receives aselect signal S, which corresponds to one of the S1-SN signals (FIG. 3).

For simplicity, only one of the memory cells 615 is shown in detail.Each of the memory cells 615 includes a latch 620 connected to a firststorage node 621 and a second storage node 622. A first access element631 connects between storage node 621 and a first bit line BL1 foraccessing storage node 621. A second access element 632 connects betweenstorage node 622 and a second bit line BL2 for accessing storage node622. Both access elements connect to a word line WL.

In some embodiments, storage nodes 621 and 622 store data incomplementary forms. For example, storage node 621 stores a datarepresented by a first voltage and storage node 622 stores a datarepresented by second voltage.

Switching unit 651 has enable and disable modes similar to that of eachof the switching units 351, 352, and 353 (FIG. 3). The signal level ofthe S signal switches switching unit 651 between the enable and disablemodes. In embodiments represented by FIG. 6, none of the memory cells isdefective. Thus, switching unit 651 is switched to the enable mode.

In operation, certain signal level of the signal on word line WLactivates access elements 631 and 632. Access element 631 transfers thedata between storage node 621 and bit line BL1. Access element 632transfers data between storage node 622 and bit line BL2. A data pathsuch as data path circuit 133 (FIG. 1) carries the data transferred toand from storage nodes 621 and 622.

FIG. 7 shows the switching unit and the multiple memory cells of FIG. 6in which at least one of the memory cells has a defect. In FIG. 7,memory cell 715 is defective; other memory cells are not defective.Resistance symbol R7 represents a defect in memory cell 715. In someembodiments, R7 represents a defect caused by a circuit short betweeninternal nodes 611 and 612.

Since memory cell 715 is defective, switching unit 651 is switched tothe disable mode to isolate internal node 611 from supply node 601,thereby isolating memory cell 715 from supply node 601. Sincenon-defective memory cells 615 also connect to internal node 611, theyare also isolated from supply node 601.

In some embodiments, each of the memory cells 615 and 715 connects tosupply node 601 through a separate switching unit. Thus, in thoseembodiments, non-defective memory cells such as memory cells 615 are notisolated from the supply node when one or more other memory cells aredefective.

FIG. 8 shows multiple memory cells connected between two switching unitsaccording to an embodiment of the invention. The embodiments representedby FIG. 8 are alternative embodiments represented by FIG. 6. In FIG. 8,an additional switching unit 851 connects between internal node 612 andsupply node 602. Switching unit 851 has enable and disable modes similarto that of switching unit 651. A select signal X switches switching unit851 between the enable and disable modes. The X signal can be the sameversion or a derivative of the S signal.

In some embodiments, at least one of the memory cells 615 has a defectsuch as that of memory cell 715 (FIG. 7). In FIG. 8, when one of thememory cells 615 has a defect, either one or both of the switching units615 and 851 is switched to the disable mode to isolate memory cells 615from one or both of the supply nodes 601 and 602.

FIG. 9 shows a switching unit and a memory cell according to anembodiment of the invention. Switching unit 951 includes a transistor952 having a source and a drain connected between a supply node 901 andan internal node 911, and a gate for receiving the S signal. Transistor952 is a p-channel transistor. However, transistor 952 can be ann-channel transistor. Other types of transistors can also be used.

A memory cell 915 includes a latch formed by a first transistor pair 941and a second transistor pair 942. Transistor pair 941 has a common drainconnected to storage node 921 and a common gate connected to storagenode 922. Transistor pair 941 forms a first inverter with an output nodebeing the common drain and the input node being the common gate.Transistor pair 942 has a common drain connected to second storage node922 and a common gate connected to first storage node 921. Transistorpair 942 forms a second inverter with an output node being the commondrain and the input node being the common gate. Transistor pairs 941 and942 also connect together at internal nodes 911 and 912.

Switching units 951 corresponds to one of the switching units 351, 352,and 353 (FIG. 3). Memory cell 915 corresponds to one of memory cells 315(FIG. 3) and one of the memory cells 615 (FIG. 6). The internal nodesand the supply nodes in FIG. 9 correspond to that of FIG. 3.

In FIG. 9, transistor 952 turns on and off based on the signal levels ofthe S signal. Transistor 952 turns on to connect memory cell 915 tosupply node 901. Transistor 952 turns off to isolate (disconnects)memory cell 915 from supply node 901. In some embodiments, transistor952 turns off when one of the memory cells 915 has a defect.

In some embodiments, transistor 952 has a resistance such that thevoltage of internal node 911 is reduced from an initial voltage value toa reduced voltage value when a defect exists in one of the memory cells915. In some embodiments, the reduced voltage value is sufficient toindicate a circuit short between the internal nodes 911 and 912.

FIG. 10 shows the switching unit and the memory cell of FIG. 9 in whichone of the memory cells has a defect. In FIG. 10, the resistance symbolR10 represents a defect in one of the memory cells 915. In someembodiments, R10 represents a circuit short between internal nodes 911and 912. Since memory cell 915 is defective, switching unit 951 isswitched to the disable mode to isolate internal node 911 from supplynode 901, thereby isolating the defective memory cell 915 from supplynode 901.

FIG. 11 shows a memory cell connected between two switching unitsaccording to an embodiment of the invention. The embodiments representedby FIG. 11 are alternative embodiments represented by FIG. 9. In FIG.11, an additional switching unit 1151 connects between internal node 912and supply node 902. Switching unit 1151 includes a transistor 1152having a source and a drain connected between supply node 902 andinternal node 912 and a gate for receiving a select signal Y. The Ysignal can be an inverse of the S signal. Transistor 1152 is ann-channel transistor. However, transistor 1152 can be a p-channeltransistor or other types of transistors.

In some embodiments, at least one of the memory cells 915 has a defectsuch as a defect represented by resistance R10 (FIG. 10). In FIG. 11,when one of the memory cells 915 has a defect, either one or both of thetransistors 952 and 1152 turns off to isolate memory cells 915 from oneor both of the supply nodes 901 and 902.

FIG. 12 shows a system according to an embodiment of the invention.System 1200 includes a first integrated circuit (IC) 1202 and a secondIC 1204. ICs 1202 and 1204 include semiconductor devices. In someembodiments, ICs 1202 and 1204 include processors, controllers, memorydevices, application specific integrated circuits, and other types ofintegrated circuits. In embodiments represented by FIG. 12, IC 1202represents a processor and IC 1204 represents a memory device. Processor1202 and memory device 1204 communicate using address signals on lines1208, data signals on lines 1210, and control signals on lines 1220. Insome embodiments, memory device 1204 has elements similar to theelements of memory device 100 (FIG. 1), lines 1208 corresponding tolines 108, lines 1220 corresponding to lines 120, and lines 1240corresponding to lines 140.

System 1200 of FIG. 12 includes computers (e.g., desktops, laptops,hand-helds, servers, Web appliances, routers, etc.), wirelesscommunication devices (e.g., cellular phones, cordless phones, pagers,personal digital assistants, etc.), computer-related peripherals (e.g.,printers, scanners, monitors, etc.), entertainment devices (e.g.,televisions, radios, stereos, tape and compact disc players, videocassette recorders, camcorders, digital cameras, MP3 (Motion PictureExperts Group, Audio Layer 3) players, video games, watches, etc.), andthe like.

CONCLUSION

Various embodiments of the invention provide circuits and methods forrepairing defects in memory devices. Some embodiments of the inventionsprovide circuits and methods for repairing circuit shorts involvingsupply nodes of memory devices. Some embodiments of the inventioninclude a memory device having a memory array connected to a supply nodethrough a supply control circuit for receiving a supply source. When thememory array has a defective memory segment, the supply control circuitisolates the defective memory segment from the supply source to savepower. The memory device replaces the defective memory segment with aredundant segment so that the memory device still has the full storagecapacity. Other embodiments of the invention include a method ofrepairing a memory device. The method includes determining a conditionof a plurality of memory segments. When a memory segment is defective,the method electrically disconnects the defective memory segment from asupply source. The method further replaces the defective memory segmentwith a redundant segment to maintain the full storage capacity of thememory device. Some other embodiments of the invention are described andclaimed.

Although specific embodiments are described herein, those skilled in theart recognize that other embodiments may be substituted for the specificembodiments shown to achieve the same purpose. This application coversany adaptations or variations of the embodiments of the invention.Therefore, the embodiments of the invention are limited only by theclaims and all available equivalents.

1. A device comprising: a first supply node and a second supply nodedifferent from the first supply node, the second supply node coupled toa different source from that of the first supply node; a supply controlcircuit including a first plurality of switching units coupled betweenthe first supply node and a first plurality of internal nodes, thesupply control circuit further including a second plurality of switchingunits coupled between the second supply node and a second plurality ofinternal nodes; a plurality of memory segments, each of the memorysegments being coupled between one internal node included in the firstplurality of the internal nodes and one internal node included in thesecond plurality of internal nodes; and at least one redundant segmentcoupled to the memory segments operable to maintain a storage capacityof the device.
 2. The device of claim 1, wherein at least one of thememory segments is defective.
 3. The device of claim 1, wherein at leastone of the memory segments has a circuit short between one of theinternal nodes and the second supply node.
 4. The device of claim 1,wherein at least one switching unit of the first plurality of switchingunits includes a transistor having a source and a drain, the sourcebeing directly coupled to the first supply node and the drain beingdirectly coupled to one internal node included in the first plurality ofinternal nodes and being directly coupled to at least one memory cellincluded in one of the memory segments.
 5. The device of claim 4,wherein at least one switching unit of the second plurality of switchingunits includes a transistor having a source and a drain, the sourcebeing directly coupled to the second supply node and the drain beingdirectly coupled to one internal node included in the second pluralityof internal nodes and being directly coupled to at least one memory cellincluded in one of the memory segments.
 6. The device of claim 1,wherein each of the memory segments includes a plurality of memorycells, each of the memory cells being coupled between one internal nodeincluded in the first plurality of the internal nodes and one internalnode included in the second plurality of internal nodes.
 7. The deviceof claim 6, wherein at least one of the memory segments has a defectivememory cell.
 8. The device of claim 6, wherein at least one of thememory segments has a circuit short in one of the memory cells betweenone of the internal nodes and the second supply node.
 9. A systemcomprising: a processor; and a static random access memory devicecoupled to the processor, the static random access memory deviceincluding: a first supply node operable to provide a supply source, anda second supply node different from the first supply node, the secondsupply node coupled to a different source from that of the first supplynode; a memory array having multiple memory segments, each of the memorysegments being coupled to the first supply node via a supply path andoperable to receive the supply source; a supply control circuit operableto isolate a selected memory segment of the multiple memory segmentsfrom the first supply node when the selected memory segment isdefective, the supply control circuit including a first switching unitcoupled between the selected memory segment and the first supply nodeand a second switching unit coupled between the selected memory segmentand the second supply node; and a redundant array operable to replacethe selected memory segment when the selected memory segment isdefective.
 10. The system of claim 9, wherein each memory segment of themultiple memory segments couples in series with the supply controlcircuit and the first supply node.
 11. The system of claim 10, whereinthe first switching unit includes a first transistor having a sourcedirectly coupled to a memory cell of the selected memory segment and adrain directly coupled to the first supply node, and the secondswitching unit includes a second transistor having a source directlycoupled to the memory cell of the selected memory segment and a draindirectly coupled to the second supply node.
 12. The system of claim 9,wherein at least one of the memory segments is defective.
 13. The systemof claim 9, wherein at least one of the memory segments has a circuitshort to the supply node.
 14. A method comprising: placing a firstswitch between a memory segment and a first supply node; placing asecond switch between the memory segment and a second supply nodedifferent from the first supply node, the second supply node coupled toa different source from that of the first supply node; and disabling atleast one of the first and second switches to prevent the memory segmentfrom receiving a supply source at one of the first and second supplynodes.
 15. The method of claim 14, wherein the memory segment includes acircuit short to one of the first and second supply nodes.
 16. Themethod of claim 14 further comprising: storing memory addressesassociated with memory cells of the memory segment.
 17. The method ofclaim 16, wherein the memory addresses are stored in a programmable unitof a memory device, wherein the memory segment is contained in thememory device.
 18. The method of claim 14, wherein placing the firstswitch includes placing a transistor between the memory segment and thefirst supply node.
 19. The method of claim 18, wherein disabling atleast one of the first and second switches includes turning off thetransistor.
 20. A method comprising: receiving an input address;comparing the input address with a stored address; accessing a memorysegment in a memory array when the input address and the stored addressare mismatched; accessing a memory segment in a redundant array when theinput address and the stored address are matched, wherein the memoryarray includes a memory segment having a circuit short to at least oneof a first supply node and a second supply node, the second supply nodebeing different from the first supply node, the second supply nodecoupled to a different source from that of the first supply node; anddisabling at least one switching unit of a first switching unit and asecond switching unit, the first switching unit coupled between thefirst supply node and the memory segment, the second switching unitcoupled between the second supply node and the memory segment.
 21. Themethod of claim 20, wherein the input address is based on an addressreceived from address lines of a memory device.
 22. The method of claim21, wherein the stored address is stored in a programmable unit in thememory device.
 23. The method of claim 20 further comprising:transferring data between the memory segment in the memory array and adata path circuit via a first plurality of lines when the input addressand the stored address are mismatched.
 24. The method of claim 23further comprising: transferring data between the memory segment in theredundant array and a data path circuit via a second plurality of lineswhen the input address and the stored address are matched.